This document addresses how to troubleshoot the basic functionality of
the digital signal processor (DSP) from a hardware and software perspective.
This allows you to ensure that calls can be established correctly. The main
issues on the DSP are seen on the High Density Voice Network Module (NM-HDV).
The DSP is the main piece in VoIP and is responsible for the transfer of analog
to digital signals, as well as digital to analog signals. The DSP also sets the
gain and attenuation parameters, voice activity detection (VAD), compression,
and more.

The current document is tested on Cisco IOS®
Software Release 12.3(7)T and later. For information on the Cisco IOS support
for platforms which support the NM-HDV, refer to the "Platform Support Matrix
for NM-HDV" section of
Understanding
High Density Voice Network Modules.

The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.

The show
voice dsp command provides information on which timeslot
is associated with which DSP and on which particular channel of that DSP. The
command also provides the current state, CURR
STATE, of the DSP channels. For example,
IDLE indicates there is no call on that channel.
BAD indicates that there is something wrong with
that DSP channel.

Once you configure the ds0-group
command and reload the router on the NM-HDV, the timeslots of the
ds0-group
command are associated to the channels on the NM-HDV. However, if you reload
the router, the router can select different DSP channels for the
timeslots.

From enable mode, issue the test dsp <slot
number> command (hidden) in order to test the DSP.
The slot number is where your NM-HDV resides and is the same as the voice-card
value seen in the configuration. This command output is from the
test dsp <slot number>
command (hidden):

Note: A hidden command is one that cannot be parsed with a "?", and the Tab
key cannot be used to auto-complete the command. Hidden commands are not
documented, and some of the output is used strictly for engineering purposes.
Hidden commands are not supported by Cisco Systems, Inc.

If you select option 1 from the menu, you trigger the
Cisco IOS software to ping and then wait for a
response from the DSP. If a response is received, then a message is generated
that declares the DSP is ALIVE. If the Cisco IOS
software did not receive a response, the message dsp is not
responding is generated. This is the command output generated
after you select option 1 from the menu:

Note: In some of the earlier Cisco IOS releases, you can only use option 1
from the test dsp <slot number>
command. If you select other options, you cause the router to
reload or other problems to occur.

Note: If you console to the gateway, Logging console must
be enabled in order to see the command output. If you Telnet to the router,
terminal monitor must be enabled in order to see the command
output.

In the output presented, all of the DSPs are
ALIVE except DSP number 8, which shows
not responding. This indicates that the DSP is
faulty, and can be due to either a hardware or software issue.

If you run Cisco IOS software earlier than release 12.2(6a), or your
Cisco IOS software has a DSP version earlier than 3.4.49, then the problem can
be either a hardware or a DSPWare issue related to Cisco bug ID
CSCdu53333
(registered customers only)
.
If this is the case, you need to upgrade your software.

Note: As part of the Cisco
CSCdu53333
(registered customers only)
fix, a recovery code is included. When a
voice telephony security parameter (VTSP) timeout message is generated by Cisco
IOS, the DSP resets in order to recover the cause of the timeout. This happens
because most of the time, the timeout occurs on the NM-HDV when the DSP does
not respond.

If the same DSP still does not respond after the appropriate software
upgrades, then this is a hardware issue. In this case, you need to replace the
Packet Voice DSP Module (PVDM-12) on the NM-HDV where the faulty DSP is
located. Alternatively, you can simply replace the whole NM-HDV.

NM-HDV has five SIMM sockets (called Banks) that hold the PVDM-12
cards. Each PVDM-12 card contains three TI 549 DSPs. Each Bank has a LED in the
back of the NM-HDV. When there is a PVDM-12 card installed in the SIMM, the LED
is solid green.

The DSP IDs on the NM-HDV PVDM-12 (Packet Voice DSP Module) are:

The DSPs on the PVDM-12 on SIMM socket 4 have an id=
1,2,3.

The DSPs on the PVDM-12 on SIMM socket 3 have an id=
4,5,6.

The DSPs on the PVDM-12 on SIMM socket 2 have an id=
7,8,9.

The DSPs on the PVDM-12 on SIMM socket 1 have an
id=10,11,12.

The DSPs on the PVDM-12 on SIMM socket 0 have an
id=13,14,15.

If you run Cisco IOS software that has the fix for Cisco bug ID
CSCdu53333
(registered customers only)
and you still notice that the DSPs do not
respond or do not show up, open a case with Cisco Technical Support and request
an engineer troubleshoot the problem. In some cases when the DSP is faulty, the
show
voice port summary command shows an operation status of
down.

There is an issue on the NM-HDV on the Cisco 3660 router. This issue is
addressed in Cisco bug ID
CSCdw55105
(registered customers only)
.
After the router is reloaded, some channels stick in EM_PENDING mode. This
issue could be related to the DSP. If the router appears with this problem,
this issue does not happen again. This issue is seen on the Cisco IOS Software
Releases earlier than 12.2(9.3)T. If you upgrade the Cisco IOS image to Cisco
IOS Software Release 12.2(9.3)T or later, the issue is usually resolved. Also
check for the related known Cisco bug ID
CSCdw55169
(registered customers only)
.

Note: The show diag EXEC CLI command for the
NM-HDV voice Network Module might not indicate how many PVDM-12 DSP cards are
installed. This issue is documented in Cisco bug ID
CSCef45173
(registered customers only)
. For more details on any of the commands
in this document, use the
Command Lookup Tool
(registered customers only)
.

Cisco has published a DSP calculator on Cisco.com that helps simplify
the calculation. The tool requires information such as the platform type, Cisco
IOS release number, Voice Interface Card (VIC) slot configuration, and the type
of codecs to be used on these interfaces. The tool then displays the number of
DSPs required to run the configuration and generates the configuration required
in order to start the system. Refer to the
DSP
Calculator
(registered customers only)
in order to see the DSP Resource Calculator
application.